Hormone-resistant prostate cancer cells display an elevated transcription of the P450C24 gene that results in increased oxidative degradation of 1,25VD (bioactive vitamin D) and an associated decrease in the hormone's anti-proliferative and proapoptotic actions. The positive-regulatory element in the P450C24 promoter will be located and characterized through the generation of deletion constructs using the luciferase reporter gene. Functionality of the regulatory site will be confirmed by site-directed mutagenesis. Trans-regulatory protein(s) which interacts with the cis-regulatory element will be identified by DNA-affinity chromatography and mass spectrometry. Functionality of the regulatory protein(s) will be confirmed by overexpression of the protein in control prostate cell lines. Non-malignant prostate cells expressing the regulatory element will have elevated levels of P450C24 gene expression and will thereby be less responsive to 1,25VD and its ability to regulate growth, as seen in prostate cancer cells. Development of therapeutic agents that down-regulate P450C24 will sustain intraprostatic 1,25VD levels and suppress the development of prostate cancer.